Near-infrared integral field spectroscopy of young late-M and early-L dwarfs close to the deuterium-burning boundary

We report the first results of a uniform high-quality spectral characterization of 8 young late-M and early-L dwarfs in the near-infrared (1.1-2.45 μm) with the integral field medium-resolution (R=1500-2000) spectrograph SINFONI. Our targets are companions to stars, or free-floating objects members of young (< 100 Myrs) associations. The sample noticeably includes the companion to AB Pic, which is known to lie at the deuterium-burning boundary (13.6 M_{Jup}). A comparison of the spectrum of AB Pic b with empirical libraries of young late dwarfs spectral standards and to synthetic atmosphere spectra yielded the spectral type, the surface gravities (log(g)) and the effective temperature (T_{eff}) of the source. By combining T_{eff}, log(g), the observed photometry, the surface fluxes from atmosphere models and the known distance of AB Pic A, we derived new masses, luminosities and radii estimates that were carefully compared to evolutionary models predictions.